1. Field of the Invention
This invention generally relates to print ribbon cartridges for printers and typewriters, and more particularly to a print ribbon cartridge having a document guide.
2. Prior Art
A computer printer is a device used to record the output of a computer in a permanent form. Although this is a simple and straightforward premise, the actual process of transcribing computer-generated information onto paper is not easy. An assortment of electrical and mechanical components (as well as optical and chemical components in some cases) work together to form printed pages correctly and reliably.
One of the more popular printing technologies in use today is impact printing. The technique of impact printing is just as the name implies--characters (or graphics) are physically struck onto a page through an inked ribbon. Several types of impact printers are known. Many include a fixed platen and a movable print head carriage including a plurality of spaced print wires which are selectively activated and driven into a ribbon and the paper as the head moves across the paper. Because print wires can be fired in any combination, it is possible to print more than one font style, as well as custom characters or graphics.
In these wire matrix or dot matrix computer printers, the printing mechanism is positioned very close to the platen. An inked ribbon is also positioned very close to the print head, between the print head and the platen. The paper which rests against the platen has very little clearance between the surface of the platen and the ribbon. While this is an excellent arrangement for high speed matrix printing, it leads to difficult paper insertion because of the very limited space between the ribbon and the platen.
Further, a moving print head carriage has a tendency to snag on portions of paper inserted in a printer. This snagging potential is especially prevalent at edges of paper such as multiple part forms and at "outfolds" where sections of continuous fan-fold paper are connected by flexible paper hinges which project out from the platen and into the moving print head. These printers also have difficulty handling multipart carbon forms like sheet paper, order forms, and charge forms. The forms can easily crumple up inside the printer causing user annoyance as well as damage to the printer.
As such, there have been a number of attempts to solve this problem through devices for guiding the paper in printing equipment during paper transport. For example, document guides have been incorporated into the typewriter or printer itself, such as that seen in U.S. Pat. No. 4,444,522.
Unfortunately, these type of paper guides increase the cost of fabrication and assembly of the printer. In addition, should the prior art paper guide attached to the printer break, the entire printer would likely have to be transported to a service establishment for repair.
Paper guides have also been incorporated into the ribbon cartridge, but the cartridge travels with the print head and leaves a larger width of the document unguided.
Japanese patent 61-228978, entitled Ink Ribbon Cartridge, shows a ribbon cartridge having an expandable ribbon guide for protection of the ribbon from contamination. The ribbon guide has a window for exposing a part of the ribbon for printing.
Although the patent shows an accordion like ribbon guide, it does not teach nor suggest a ribbon cartridge having a document guide as is taught and claimed herein.
U.S. Pat. Nos. 5,074,689 and 5,098,208 both entitled Ribbon Cassette with Integral Paper Guide, show a ribbon cartridge having a platen like curved member along the front of the cartridge for guiding paper between the print head and the print platen.
Although these patents show a ribbon cartridge having an integral paper guide, they do not teach nor suggest a ribbon cartridge having a document guide as is taught and claimed herein.